The Clock of Doom is now reading two years and counting for Microsoft's XP operating system. On Monday, the software giant announced its "two-year countdown" for the venerable platform, as it tries yet again to get users to upgrade.

On April 8, 2014, Microsoft will officially end all support for XP, as well as for Office 2003, including all new security patches, non-security hotfixes, free or paid assisted support options, or online technical content updates. On its Windows blog, Director of Marketing Stella Chernyak wrote Monday that, "if you still have some PCs running Windows XP and Office 2003 in your organization, now would be a good time to start migrating them to Windows 7 and Office 2010."

'You Are Late'

Microsoft's Web site goes further. "If your organization has not started the migration to a modern PC, you are late," it said, because the average enterprise deployment can take 18 to 32 months "from business case through full deployment."

Chernyak described XP and Office 2003 as "great software releases for their time," but noted the rapid evolution of technology. Microsoft is recommending that companies upgrade now to Windows 7 and Office 2010, while there still is support for the older versions.

XP retains its popularity among many consumers and businesses, as a steady -- albeit limited -- platform. Given the lifespans of operating systems, XP is an elderly Methuselah, having gone on sale in the fall of 2001. When its life support is finally discontinued in two years, it will have been backed by the company about 30 months longer than the next oldest OS, Windows NT.

Charles King, an analyst with Pund-IT, described XP to us as "a terrific OS, very stable." He said companies "tend to migrate to new technologies when there are technical benefits to doing so," adding that he thought Windows 7 offered those benefits.

'Serious Issues' with 8

But, King noted, "there are going to be serious issues" that businesses will have to address if they migrate to the coming Windows 8, which will have a classic Windows interface but is mostly oriented toward a tile-based interface designed for tablets and other touchscreens.

The company's two-year reminder is not Microsoft's first attempt to move reluctant users to a newer platform. In summer of last year, for instance, a Windows community manager wrote on the Windows blog that it's time for XP users "to move on," following the platform's "amazing run."

Microsoft has pointed out that, when it is no longer supported with security fixes, XP will become much more vulnerable to threats. In addition, third-party application providers are not expected to continue their support for apps designed for XP.

Early last year, Microsoft announced that its then-new Internet Explorer 9 would not run on XP, which it called "the lowest common denominator."

A year ago, Web metrics firm Net Applications reported that XP was running on 51 percent of all the computers on the planet. Among businesses, according to Forrester Research, that figure was closer to 60 percent.

In the last year, XP has lost about 10 percent of its market share, and, at its current pace of decline, is projected to drop to about 17 percent of the market by the time the Clock of Doom sounds its alarm in April 2014.

But cheer up, XP. Your younger sibling, the 5-year-old Vista, is also being cut off from the family tree. Starting Tuesday, security updates for Vista will continue to be free, but any Vista user without a commercial support contract will have to pay for non-security bug fixes and other patches. After April 1, 2017, there will be no more security updates for Vista.